Circuit interrupting system



July 5, 1932. c, PRINCE 1,866,371

CIRCUIT INTERRUPTING SYSTEM Filed Oct. 1, 1929 AAA/,3 T vvv FL Q3. S M w V Inventor:

FL 6 David C.Prince,

haw/527m His Attorneg Patented July 5, 1932 UNITED STATES PATENT OFFICE DAVID C. PRINCE, OF SCHENECTADY, NEW YORK, ASSIGNOR TO GENERAL ELECTRIC- COMPANY, A CORPORATION OF NEW YORK CIRCUIT IN TERRUPTIN G SYSTEM Application filed Getober 1, 1929. Serial No. 396,548.

My invention relates to circuit interrupting systems, and more particularly to the use of high vacuum fuses in such systems. I

In the interruption of large power currents at high tension by the usual oil circuit brealv on an unusually large overload or short circuit, with the result that the sustained arcing between the switch contacts usually causes destruction of the switch and in some cases,

great damage .to adjoining switchgear.

It is a principal object of my invention to provide means for inserting auxiliary interrupting means into the circuit of the main circuit breaker at a point where the main switch has normally cleared the circuit.

It is a turtherobject of my invention to provide means which shall be actuated by and in accordance with the movement of the movable contact structure of the main circuit breaker for inserting a high vacuum high tension fuse in the circuit of the breaker at a point in the opening travel of the contact structure where the circuit is normally cleared.

My invention will be more fully set' forth in the following description referring to the accompanying drawing and the features of novelty which characterize my invention will be pointed out with particularity in the claims annexed to and forming a part of thisspecification. p

This application is a continuation in part of my copending application, Serial No. 264,117, filed March 23, 1928.

Referring to the drawing, Fig. 1 is a diagrammatic illustration of a circuit interrupting system embodying my invention;

. Fig. 2 illustrates a more specific formthereof,

and Fig. 3 illustrates a modified form of the system shown in Fig. 2.

In Fig. 1, and more specifically in Fig. 2,

there is illustrated a main circuit breaker 1,

which may be of large interrupting capacity as in the fluid-break or oil type. Thebreaker is provided with operating mechanism.2 of any suitable type having an operating rod 3 for engaging through mechanism (not shown), the movable bridging member of the breaker with the stationary contacts 5. In the normal opening operation the bridging member 4 is tripped by suitable means and during its initial opening movement draws a power are between the contacts, which is usually extinguished by the insulating fluid in which the contacts are immersed when the bridging member has opened to a predetermined extent. lVhen'the main circuit breaker is not called upon to interrupt exceptionally heavy currents the above described operation is generally sufficient to clear the circuit and the arcis extinguished'when the bridging member has moved to its open position. i

In the event, however, that the main circuit breaker is called upon to interrupt an unusually large current, as a heavy short circuit, it may happen that the arc is not extinguishcd even when the bridging member has reached its fully open position. The .sus tained arcing within the switch casing usually setsfire to the oil, if this insulating fluid is used, and generates disruptive pressures within the switch generally causing destruction of the same and damage to adjoining switch gear.

For thepurpose of clearing the circuit in g the event that the main circuit breaker fails to do so, I provide auxiliary circuit interrupting means which is inserted in the circuit of the main switch at a point in the open ing movement thereof where it has normally cleared the circuit. T 0 this end, as is illustrated in Figs. 1 and 2, a high ension high' vacuum fuse (3, which has a circuit interrupting capacity comparable with or greater thanv that of the main'breaker, is connected in series with the main switch and is normally shunted by auswitch 7 which may be of the air-break or any other suitable type. hen the main switch is closed the shunting switch 7 carries practically all of the line current, very little current passing through the fuse 6. The. switch 7 is normally biased to open position, as by'a spring 8, and isadapted to be latched in its closed positionby a latching element 9.having an arm extending in the line of travel of a trip member 10 mounted on the operating rod 3 of the breaker.

ment of the bridging member. In the open-- ing operation of the main breaker the bridging member 4 and the operating rod 3 both descend with the result that the trip member 10 engages the latch 9 at a predetermined point in the opening movement of the brid ing member, at which point it hasnormal y cleared the circuit, to release the latch ng means and to permit the switch 7 to open under the influence of the spring 8, thereby placing the high tension high vacuum fuse- 6 directly in series with the breaker.

Since the type of circuit breaker as illustrated is generally used in an alternating current system, the fuse 6 is preferably. of the high tension high vacuum alternating current type and may be of the character described and claimed in a copending application, Serial No. 264,113, filed March 23, 1928,

by myself and Bertram Wellman. This type of. fuse is described in complete detail in the above application a'n'd comprises fuse supporting electrodes or terminals 6 which are.

composed of a metal havin a comparatively low melting point incapable of thermionic emission. The terminals may be made of copper, nickel or silver, and aluminum also may be used. Upon rupture of the fusible element in response to excessive current the ter-' minal which is the cathode at the time of rupture has formed then on a cathode spot at the point where the fusible element was connected to the electrode. The creation of this cathode spot causes flow of electrons to the anode, this'fiow of electrons continuing until the current has reached the zero value in the cycle at which time the electron flow immediately ceases due to'reversal of the current. The electrode which was formerly the anode is now the cathode, and since the conditions originally present for creating a cathode spot do not now obtain, there will be no flow of electrons in the opposite direction. Accordingly, there will be a lapse of one-half cycle during which time there is no electron flow across the terminals of the fuse and this lapse of time is sufficient to prevent reestablishment of a cathode spot on the electrode which was the ori inal cathode,

Insertion of the igh tension high vacuum fuse directly in series with the main breaker at a point where it has normally cleared the circuit therefore prevents the fuse from being unnecessarily blown and at the same time provides additional protection for the system in the event that the main breaker has not cleared the circuit after a reasonable opening travel of the bridging member.

chanically. The fuse 6 is shunted as in the formerinstance by the switch 7 biased towards its open position and maintained in its closed position by a relay controlled latching device 12. 'Energization of-the device 12 to release the latch and'to insert the fuse 6 in the circuit ma be effected through the usual current trans oi-mer 13 upon opening of the short circuiting switch 14 1n response to opening movement of the main breaker, In the event, however, that the main circuit breaker has properly cleared the circuit by the time the short-circuiting switch 14 has opened, the switch 7 is. not tripped, as the device 12 cannot be energized by the current transformer, so that automatic or other reclosing means is not needed.

It shall be understood that my invention is not limited to the specific apparatus and arrangement thereof herein illustrated, and that various modifications and changes thereof may be made without departing from the spirit of my invention.

What I claim as new and desire to secure by Letters Patent of the United States, is,

1. 'A circuit interrupting system comprising in combination, a main circuit breaker for normally interrupting the circuit, an auxiliary circuit interrupting device having'an interrupting capacitycomparable with that of said main breaker, and means for inserting said auxiliary device in the circuit in series with said breaker only after predetermined opening of said breaker, the circuit being open and normally interrupted by said breaker at said predetermined opening.

2. A circuit interrupting system comprising in combination a main circuit breaker,

an auxiliary circuit interrupting device havin g an interrupting capacity comparable with that of the main breaker, and means actuated in response to opening movement of the main breaker for inserting the auxiliary device in' series in the circuit of said breaker at a point where the main breaker is in open circuit position and has normally cleared the circuit. 3. A circuit interrupting system comprisingin combination a main circuit breaker, a high tension high vacuum fuse having an interrupting capacity comparable with that of the main breaker, and switching means actuated 'in response to opening movement of the breaker for inserting said fuse in the circuit of the breaker at a point where said breaker is in open circuit position and has normally cleared the circuit.

4. In a circuit interrupting system, a main circuit breaker, a high tension hi vacuum fuse havin an interrupt' rablewith at of the main or connected caacitcomaat Y P in the system, switching means for normally Y shunting said fuse and adapted to carry the current traversing the main breaker, and

means actuated in response to opening movement of the ma n breaker when it has reached a point where it has normally cleared the circuit for opening the shunting switching means, thereby inserting the fuse in the breaker circuit.

5. In a circuit interrupting s stem, an oil circuit breaker, a high tension igh vacuum fuse of the alternating current type havin an interrupting capacity comparable wit a that of said breaker connected in said system, a switch connected in shunt with said fuse for normally carrying the current traversing the main breaker, and means actuated by and in accordance with opening movement of the main breaker for opening said switch and placing the fuse in series with the breakoint the er,. said means being actuated at a where the breaker has normally cleare circuit.

6. The combination of an electric circuit, a

a switch for opening and closing the circuit, a high vacuum fuse in series with said switch, a second switch arranged to open and'close a shunt circuit around said fuse and .means whereby opening of the first switch opens the second switch to'insert the fuse in circuit to interrupt the circuit in the event that the first switch fails to clear the circuit.

7. The combination of an electric circuit, a main switch for opening and closing the circuit, a high vacuum fuse in series with said switch, and a switch arranged to open and close a shunt circuit around said fuse, said switch coacting with said main switch to insert the fuse in series with the main switch only upon failure of said main switch properly to clear the circuit.

8. A circuit interrupting system compris-.

ing a main circuit breaker for normally interrupting the circuit, an auxiliary circuit interruptng device having an interrupting capacity comparable with that of saidbreaker, a switch normally shunting said auxiliary device arranged to insert said device in the clrcuit 1n serles with said breaker, and means actuated by said breaker for opening said switch and inserting said auxiliar device in the circuit only after said breaker as opened to a position where it has normally interru ted the circuit.

11 witness whereof I have hereunto set my hand this 30th day of September, 1929.

DAVID C. PRINCE. 

